android - invalidateOptionsMenu 在 fragment 中不起作用

Question

我想根据编辑文本中的文本是否显示或隐藏操作栏中的项目

所以我做了以下

            public class NounSearch extends  android.app.Fragment 
{

EditText seachEditText;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState)
    {
            super.onCreate(savedInstanceState);
            View rootView = inflater.inflate(R.layout.nounsearchactivity, container, false);
                    //Intiate EditText
            seachEditText =(EditText) rootView.findViewById(R.id.nounSearch);
            seachEditText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
                @Override
                public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
                    if (actionId == EditorInfo.IME_ACTION_SEARCH) {
                        searchResult.Entities = new ArrayList<NounModel>();
                        _currentPage = 0;
                        categoryId = -1;
                        new GetNouns().execute();
                        return true;
                    }


                    return false;
                }
            });
            seachEditText.addTextChangedListener(new TextWatcher() {

               public void afterTextChanged(Editable s) {
               }

               public void beforeTextChanged(CharSequence s, int start,
                 int count, int after) {
               }

               public void onTextChanged(CharSequence s, int start,
                 int before, int count) {
                 getActivity().invalidateOptionsMenu();
               }
              });

    }
    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        super.onCreateOptionsMenu(menu, inflater);

            if(seachEditText.getText().toString().length() > 0)
            {
                menu.findItem(R.id.action_search).setVisible(true);
            }
            else
            {
                menu.findItem(R.id.action_search).setVisible(false);
            }
    }





}

但actionitem永远不会出现

Answer 1

要更新 fragment 中的 onCreateOptionsMenu，您需要在 fragment 的 onCreate 方法中调用 setHasOptionsMenu(true);。否则调用 getActivity().invalidateOptionsMenu();

时将无法更新

样本:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setHasOptionsMenu(true);
}

编辑:

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        if(seachEditText.getText().toString().length() > 0)
        {
            menu.findItem(R.id.action_search).setVisible(true);
        }
        else
        {
            menu.findItem(R.id.action_search).setVisible(false);
        }
    super.onCreateOptionsMenu(menu, inflater);


}